1. Field of the Invention
The present invention relates to a spindle motor and a disk drive apparatus.
2. Description of the Related Art
A hard disk device is equipped with a spindle motor for rotating a disk. One example of conventional spindle motors is disclosed in, e.g., SG 135981. A permanent-magnet synchronous motor disclosed in SG 135981 includes a permanent magnet attached to at least one of a top yoke and a bottom yoke and an armature arranged in an air gap between the permanent magnet and the other yoke.
A so-called axial gap structure in which an armature and a permanent magnet are axially opposed to each other as in SG 135981 is more advantageous in reducing the thickness of a motor than a so-called radial gap structure in which an armature and a permanent magnet are radially opposed to each other. However, the radial gap structure and the axial gap structure differ fundamentally from each other in the arrangement of individual components within the motor. In order to increase the manufacturing efficiency and driving efficiency of the motor, it is therefore necessary for the axial gap structure to adopt structural features differing from those of the radial gap structure.